WHAT IS BREAST CANCER RISK ASSESSMENT?

By Karen Hanson, M.S., C.G.C.

The two questions that cancer risk assessment genetic counselors are most frequently asked are: "What are my chances of developing breast cancer?" and "What are the chances that the breast cancer in my family is hereditary?"

The third most popular is, "How did you figure that out?"

Genetic counseling for risk assessment is a relatively new area in the management of breast cancer. Below is an overview of cancer risk assessment counseling as it is conducted at this center.  More detailed information about hereditary, sporadic, and familial breast cancer can be found here.

Genetic counseling for breast cancer risk assessment is based upon the following tenets:

• Hereditary cancers account for only 5-10% of the total number of breast cancer cases.
• The patient's perception of risk is as important as the figure given. A woman who has watched her mother die from breast cancer may have a different feeling than a woman who has several aunts still alive and doing well after their breast cancer diagnosis and treatment.
• Women often overestimate their risk of developing breast cancer.  Patients may state at the beginning of a session, "I know that the cancer in my family is hereditary. I think I should just be tested without going through the counseling." Once a risk is given, the patient may be confused about why it is lower (or higher) than she originally believed.
• Risk assessments are given with a comparison to the age-specific risk that all women, regardless of family history, have for developing breast cancer.
• Breast cancer risk does not exponentially increase every year, but incrementally after age 50.
• Currently, gene testing is available only for mutations in two breast cancer genes, BRCA1 and BRCA2.
• The counseling session includes a discussion of surveillance techniques and lifestyle options that may reduce a woman’s risk of developing breast cancer.
• The calculated risk estimates are for developing breast cancer, not dying of it.

Many women seeking genetic counseling have already been diagnosed with breast cancer.  They are often primarily concerned about the chance to carry an inherited gene mutation, the risks to other family members, and their own chances of being diagnosed with a second cancer.  Genetic counselors help these clients decide if genetic testing is appropriate for them by determining their chance of testing positive for a gene mutation and by discussing the risks, benefits, and limitations of genetic testing.

The Risk Assessment Models

Several mathematical risk assessment models are used to calculate breast cancer risk. Some of these computer programs are available to counselors, and are used according to the circumstances of each individual patient.  Since each model has advantages and disadvantages, more than one model may be used.  The counselor may also use medical literature and other sources of data in arriving at a risk figure.

The Gail Model is the best-known model for estimating a woman's risk to develop breast cancer at some time in her life. This model is based on a large number of mainly Caucasian women, ages 35-60, who attended a regular screening program.  Updated versions have been modified to include specific risks for other populations.  The Gail Model does not take into account large family histories of breast cancer or age at diagnosis, nor the presence of bilateral cancer, ovarian cancer or male breast cancer in the family.    

The Claus Model is based on the assumption that breast cancer susceptibility is related to a rare gene mutation inherited in a dominant pattern.  the Claus Model takes into account family history and age at diagnosis to generate an age-specific risk for an unaffected woman to develop breast cancer.  It does not account for more than two 1st or 2nd degree relatives, the presence of bilateral cancer, ovarian cancer or male breast cancer in the family, or other important risk factors.

The BRCAPRO (or Duke) Model is based on the probability that the patient carries a BRCA1 or BRCA2 mutation.  It incorporates family history of both affected and unaffected 1st and 2nd degree relatives, and includes bilateral breast, ovarian, and male breast cancer in the risk calculation.  In addition, it estimates the risk for a BRCA1 or BRCA2 mutation in the individual counseled.